Phenolic resins with improved low temperature processing stability

ABSTRACT

Phenolic novolak resins are described which are structurally characterized as having from about 55% to about 90% of the available theoretical paraphenyl linkages in the resin chain bridged to a phenyl group. The resin compositions of this invention provide extended resin stability at relatively low temperatures without significant adverse affect on the cure speed at the molding temperature. The resins are especially suited for use in runnerless injection or cold manifold molding processes, but can also be used in transfer, compression and injection molding processes.

This is a division of application Ser. No. 030,038, filed Apr. 12, 1979,which is a continuation-in-part of application Ser. No. 915,335, filedJune 13, 1978, now abandoned.

BACKGROUND OF THE INVENTION

For many years, thermosetting phenolic resins have been molded usingstandardized compression or transfer molding techniques. While thesetechniques generally provide molded articles having excellentdimensional stability and good physical properties, technicalimprovements leading to cost reduction and increased productivity arerequired in order to enable thermosetting phenolics to remaincompetitive with other plastics and materials of constructions such asmetals and ceramics. One such improvement has been the application ofinjection molding techniques to fabricate parts from thermosettingphenolic molding compositions. The injection molding process offers theadvantages of reduced molding cycles, better control of processvariables, and increased productivity as compared with conventionalcompression and transfer molding processes. The major disadvantage withthe injection molding of thermosetting materials lies in the inevitablegeneration of a considerable amount of scrap, particularly whenemploying multiple cavity systems. This scrap represents thermosettingmaterial that has cured (become infusible) in the runner and cannot bereused. The amount of non-reusable scrap generated in this fashion canbe substantial, typically ranging anywhere from 15% to 80% of the totalamount of material required to mold a part.

A more recent technical advance in the molding art has been theadaptation of the runnerless injection, or cold manifold, process toinjection mold thermosetting phenolics. In the cold manifold process,the material in the sprue and manifold system (the so-called "runner")is maintained at a sufficient temperature to plasticize the material,without causing it to cure or "set-up" prematurely. Thus, when a curedpart is removed from the mold cavity, the material in the sprue andmanifold becomes part of the next molding, instead of being discarded asin conventional injection and transfer molding operations, therunnerless injection process, therefore, provides for significantsavings in material, and, in addition, increased industrial efficiencyby the elimination of secondary operations such as extra finishing andsecondary gate grinding.

The thermosetting materials employed in runnerless injection processesdiffer, in certain respects, from materials normally employed inconventional injection processes due to the different requirements ofeach process. One significant difference is that a standard injection ortransfer molding material typically has a stiffer plasticity for fastermolding cycles. In contrast, a runnerless injection material shouldremain in a plasticized or fused condition in the manifold or barrel ofthe mold for extended periods of time without curing prematurely at themanifold temperature, i.e.usually about 125° C., while being capable ofcuring rapidly in the mold cavity at the molding temperature, i.e.usually about 170° C. In addition, the molded part should also have gooddimensional stability and physical properties.

The prior art discloses various thermosetting compositions which aredirected to runnerless injection applications. For instance, U.S. Pat.No. 3,959,433, to Sauers, discloses the addition of non-polymericpara-substituted phenols, such as Bisphenol-A, to a thermosettingphenolic resin in order to reduce the viscosity of the resin in themanifold, i.e. to improve its processibility. This composition islimited in terms of the range of monomer or dimer employed, generallybeing less than 35 parts by weight based on 100 parts by weight ofresin, since introducing higher concentrations in the resin compositiontends to adversely affect the physical properties of a molded article bydecreasing the cross-linking density of the cured article. Moreover,this composition has not been found to be effective in significantlyimproving the processing stability of the resin at the manifoldtemperature. As this is a critical parameter in any runnerless injectionmolding process, it will readily be appreciated that a continuing needexists for improved runnerless injection materials, and, in particular,for improved materials having enhanced processing stability.

While the phenolic resins of this invention are primarily useful inrunnerless injection processes, where low temperature processingstability is a critical factor, they also find utility in moreconventional molding processes such as injection molding, extrusion, andtransfer molding processes where material savings can also be asignificant factor.

SUMMARY OF THE INVENTION

Accordingly, this invention provides a phenolic novolak resins withimproved thermal stability which are structurally characterized ashaving from about 55% to about 90% of the available theoreticalparaphenyl linkages in the resin chain bridged to a phenyl group.Suitable resins may be prepared in situ by sequentially reacting excessphenol with a ketone, in the presence of a mineral acid catalyst to forma bisphenol, and subsequently reacting the products (phenol+bisphenol)with an aldehyde to form the resin. Suitable resins can also be preparedby the reaction of bisphenol, phenol and an aldehyde. Alternatively,suitable novolak resins having a predominance of the availabletheoretical para-phenyl linkages in the resin chain bridged to a phenylgroup can be prepared by admixing (1) a novolak resin prepared bycondensing excess phenol with an aldehyde with (2) from about 10 toabout 80 parts by weight of admixture of a novolak resin prepared bycondensing excess bisphenol, preferably Bisphenol-A, with an aldehyde.The resin compositions of this invention have significantly enhancedprocessing stability at the manifold temperature of a runnerlessinjection molding apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The phenolic novolak resins of this invention are prepared fromcomponents well-known to those skilled in the plastics art. These resinsmay be prepared by a variety of methods. However, regardless of themethod of preparation employed, the resin system is characterized ashaving a predominance, or at least about 55%, preferably at least about65%, but less than about 90%, and preferably less than about 80%, of theavailable theoretical para-phenyl linkages in the resin chain bridged toa phenyl group. It will be readily appreciated that the remainingunoccupied para-phenyl positions of such resins are available forcross-linking reaction. The resin compositions of this invention haveexcellent thermal stability at the process temperature of a runnerlessinjection manifold, i.e. about 125° C. Rather surprisingly, it has beenfound that resin systems having less than about 55% of the availabletheoretical para-phenyl linkages bridged do not, in general, experiencea significant improvement in low temperature (125° C.) processingstability. Resin systems having greater than about 90% of the availabletheoretical para-phenyl linkages bridged have not been foundsatisfactory due to excessively slow curing speeds at the moldingtemperature (170° C.).

The introduction of the required predominance, i.e. between about 55%and 90%, of the available theoretical para-phenyl linkages into theresin composition is generally accomplished by introducing a p-p'bisphenolic structure into the resin composition. In one method (A), thebisphenolic structure can be introduced into a reaction mixture of aphenol and an aldehyde and/or ketone as a separate component. In anothermethod (B), the bisphenol can be formed in situ by the reaction of aketone, and preferably acetone, with the phenol, preferably phenol perse. As a typical example of the in situ method of preparation, abisphenol A structure can be introduced into a phenolic resin byreacting phenol and acetone, in a molar ratio of about 4:1 respectively,at about 0° C. to about 20° C. employing a hydrochloric acid catalyst.After removing any excess phenol, an aldehyde is added to the reactionmixture and reacted at reflux temperature to form a novolak resin havinga predominance of the available theoretical para-phenyl linkages of theresin bridged to a phenyl group.

The resins of the invention which are prepared by either of theafore-mentioned methods (A) or (B), differ from prior art resins inseveral respects. First, the resins are characterized by having shortcarbon chains linked between adjacent hydroxyl-substituted phenylnuclei. These carbon chains are generally 1 to 5 carbon atoms in length,preferably 1 to 4 carbon atoms and more preferably 1 to 3 carbon atoms.

The resins are further characterized by having phenolic groups, i.e.,hydroxyl-substituted phenyl nuclei that are capable of forming athree-dimensional network. Thus, each hydroxyl-substituted phenylnucleus is capable of chain growth at unsubstituted ortho- andpara-positions of those nuclei.

The result of employing resins having the foregoing chemicalcharacteristics is to increase the cross-linking density of the resinsto improve the thermal properties such as heat distortion temperatureand the mechanical properties such as tensile and flexural strength.

The phenols which are suitable for use in this invention include phenolper se (unsubstituted), and substituted phenols which are unsubstitutedin the para position, wherein at least about half the substitutedphenols have at least two of the ortho and para positions of the phenolnucleus available for condensation (unsubstituted). Such phenols may becharacterized by the following general formula: ##STR1## where R₁ can behydrogen, fluorine, chlorine, bromine or a suitable substituent selectedfrom the following:

a. Alkyl and alkenyl groups of 1 to 18 carbon atoms in any of theirisomeric forms and substituted on the phenolic nucleus in the ortho ormeta positions;

b. Alicyclic groups of 5 to 18 carbon atoms such as cyclohexyl,cyclopentyl, methyl cyclohexyl, butyl cyclohexyl, and the like;

c. Aromatic or aralkyl groups of 6 to 18 carbon atoms such as phenyl,alpha-methyl benzyl, benzyl, cumyl and the like;

d. Alkyl, alkenyl, alicyclic, aryl and aralkyl ketones wherein thehydrocarbon is defined as hereinbefore;

e. Alkyl, alkenyl, alicyclic, aryl and aralkyl carboxylic groups whereinthe hydrocarbon is defined as hereinbefore, and mixtures thereof.

As indicated, the hydrocarbon radicals preferably have from 1 to 18carbon atoms.

Suitable substituted phenols include meta-cresol, ortho-cresol,ortho-chlorophenol, ortho-ethylphenol, meta-butylphenol,ortho-butylphenol, and the like, as well as mixtures thereof.

The preferred phenols are unsubstituted and have both ortho and parapositions available for condensation reaction.

The bisphenols which can be used in this invention are p, p'-substitutedbisphenols and include compounds corresponding to the general formula:##STR2## wherein the R₄ substituents are located in meta positions withrespect to the individual phenyl nuclei and correspond to the R₄substituents of the substituted phenols described above; R' is hydrogen,alkyl, haloalkyl, aryl, haloaryl, alkylaryl, haloalkylaryl, arylalkyl,haloarylalkyl, cycloalkyl, halocycloalkyl or heterocyclic; X is adivalent (or di-substituted) alkylene, cycloalkylene, arylene, --O--,--S--, --SO--, --SO₂ --, --SO₃ --, --CO--, R'P<═O, or R'N<; m is aninteger from 0 to the number of replaceable hydrogen atoms on X; and nis 0 or 1. When there is more than one R' substituent in the bisphenol,such substituents may be the same or different. Preferred embodimentsinclude configurations wherein X is a single divalent carbon atom or asulfur atom, and m is 2, wherein at least one of the R' substituents ishydrogen and the other R' substituent is methyl, isopropyl, or phenyl. Aparticularly preferred embodiment is Bisphenol A, wherein X is a singledivalent carbon atom, m is 2 and both R' substituents are methyl groups.Mixtures of the above-described bisphenols may also be employed.

Examples of bisphenols which may be used in practicing this inventioninclude 2,2-bis(4-hydroxyphenyl)propane (bisphenol A),2,2-bis(4-hydroxyphenyl)methane, 2,2-bis(3-methyl-4-hydroxyphenyl)methane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)methane,2,2-bis(4-hydroxyphenyl)sulfide, 2,2-bis(4-hydroxyphenyl)oxide,2,2-bis(4-hydroxyphenyl)ketone, 2,2-bis(4-hydroxyphenyl sulfone,2,2-bis(4-hydroxyphenyl)sulfoxide, 2,2-bis(4-hydroxyphenyl)sulfonate,2,2-bis(4-hydroxyphenyl)amine, 2,2-bis(4-hydroxyphenyl)phenyl phosphineoxide, para-phenylphenol, para-benzylphenol, as well as mixturesthereof, including commercially available mixtures such as mixtures ofisomers, mixed isomer by-product streams, and the like.

The aldehydes or ketones or mixtures thereof which can be employed arethose which are capable of reacting with a phenol or bisphenol, providedthe aldehydes or ketones do not contain a functional group or structurewhich is detrimental to the condensation reaction. The preferredaldehyde is formaldehyde, which can be in aqueous solution or in any ofits low polymeric forms such as paraform or trioxane or gaseous,anhydrous formaldehyde. The aldehydes preferably contain 1 to 8 carbonatoms. Other examples include acetaldehyde, propionaldehyde,butyraldehyde, benzaldehyde, furfural, 2-ethyl-hexanal, ethylhexanal,ethylbutyraldehyde, heptaldehyde, pentaerythrose, glyoxal, chloral,mesityl oxide, and the like. The ketones have the formula: ##STR3##wherein R₂ and R₃ can be hydrogen or organic radicals. Examples ofketones are acetone, methyl ethyl ketone, diethyl ketone, methyl benzylketone, methyl cyclohexyl ketone, diallyl ketone, dichloromethyl ketone,as well as mixtures thereof. R₂ and R₃ preferably have 1 to 7 carbonatoms. The preferred ketone is acetone.

The proportion of theoretical para-phenyl linkages in the finalcondensation product can be controlled by varying the proportion ofbisphenol present in the reactive mixture of phenol and an aldehydeand/or ketone. As is known to those skilled in the art, novolak resinsformed by the condensation reaction of an unsubstituted phenol monomerand an aldehyde and/or a ketone generally have approximately 50% of theavailable theoretical para-phenyl linkages bridged to a phenyl group inthe resin chain. By replacing the unsubstituted phenol with a bisphenolin the reaction mixture, the resulting condensation product has all ofthe available theoretical para-phenyl linkages in the resin chain asp-p' bridges. However, as mentioned previously, a resin having such ahigh proportion of available theoretical para-phenyl linkages which arebridged would not be suitable for use in this invention due to extremelyslow cure speed in the mold. Accordingly, an effective amount ofbisphenol needed to provide the required proportion of para-phenyllinkages has been found to be in the range of from about 0.1 to about0.8 moles per mole of total phenolic component employed in thecondensation reaction.

The ratio of aldehyde or ketone to phenol can be varied to preparecondensates of various molecular weights, and the viscosity of the finalcondensation product can be regulated by the molecular weight of thephenol-aldehyde or phenol-ketone condensate. A low molecular weightcondensation product is generally preferred. Generally, the amount ofaldehyde or ketone varies from 0.5 to 0.9 mole per mole of phenol, andis preferably in the range of about 0.63 to about 0.68, and mostpreferably is about 0.65 to 0.67 mole per mole of phenol.

In an especially preferred embodiment, the phenolic resins of thisinvention are prepared by admixing (1) a novolak resin componentprepared by condensing excess phenol and an aldehyde, and (2) a novolakresin component prepared by condensing a bisphenol, preferablybisphenol-A, with an aldehyde. The blend or intimate mixture of thecomponents can be prepared using conventional mixing equipment, such as,for example, a Banbury mixer, ball mill, or kneader. The proportion ofeach resin component required to prepare a composition having apredominance of available theoretical paraphenyl linkages can vary fromabout 10 to about 80 parts by weight of resin component (2) per 100parts by weight of resin blend. Preferably according to this method ofpreparation, the resin component (2) is present in an amount of fromabout 20 to about 60 parts per 100 parts by weight of resin blend, andmost preferably from about 30 to 60 parts by weight.

The preferred resins of the invention are characterized as having anarrow molecular weight distribution as measured by gel permeationchromotography (GPC) and expressed as Heterogeneity Index (HI), which isthe ratio of weight average molecular weight (Mw) to number averagemolecular weight (Mn). The most preferred resins of the invention have aHeterogeneity Index in the range of about 1.5 to 2. The weight averagemolecular weight (Mw) is generally in the range of 600 to 1000, and thenumber average molecular weight (Mn) is generally in the range of about350 to 450. These resins have a low melt viscosity which is generally inthe range of about 500 to 1200 centipoises at 135° C.

In addition to these most preferred resins, other resins which can beused in the compositions of the invention have the followingcharacteristics:

    ______________________________________                                                     RESIN                                                            Characteristics                                                                              A         B         C                                          ______________________________________                                        Gel Permeation Chroma-                                                        tography (GPC)                                                                --Mw            800-1000 1000-1400 1200-1600                                  --Mn           350-450   350-450   350-450                                    Heterogeneity                                                                 Index (H.I.)   2.1-2.5   2.5-3.1   2.7-3.2                                    Melt Viscosity @ 135°                                                  (centipoises)  1500-2500 2500-4000 3000-4000                                  ______________________________________                                    

The phenolic resin compositions of this invention can be compounded withvarious additives and adjuvants, such as curing accelerators, metaloxides such as lime, ZnO, MgO and mixtures thereof; fillers such asglass fiber, wood flour, clay, talc, and the like, stabilizers,plasticizers, curing accelerators, antistatic agents, and lubricantssuch as stearic acid and glycerol monostearate.

The novolak resins of this invention are prepared with a deficiency ofaldehyde, preferably in the presence of an acid catalyst such as strongmineral or organic acids such as sulfuric acid and oxalic acid, and willonly cure or cross-link in the presence of a curing amount of a suitablealdehyde donor compound. In commercial practice, the aldehyde donorcommonly employed is hexamethylenetetramine which is blended in finelydivided form with the pulverized resin. Upon the addition of a curingamount of hexamethylenetetramine (or some other suitable aldehydedonor), the resin becomes thermosetting and will permanently fuse uponheating.

The resin, fillers, cross-linking agents, and other ingredients can bethoroughly blended by ball-milling and fused by roll-milling, extrusionor other conventional techniques. After it is fused, the moldingcomposition can be tested by curing in a Brabender Plasticorder (ASTMdesignation D-1898), an instrument which continuously measures thetorque exerted in shearing a polymer, and the time interval to the onsetof cure of the resin at a particular temperature can be measured todetermine the barrel life and the molding cycle.

Prolonging the barrel life of the resin may result in a somewhat longermolding cycle as compared to conventional resin systems due to a slowercure speed at the molding temperature. The molding cycle may beshortened by the adjustment of certain operating variables, such as byincreasing the molding temperature, or by employing a resin compositionhaving a lower proportion of available theoretical para-phenyl linkages.

The following examples further illustrate the various aspects of theinvention but are not intended to limit it. For instance, in accordancewith known practice, the molding composition may also include additionalappropriate ingredients including pigments, lubricants, mold releaseagents and the like. Where not otherwise specified in this specificationand claims, temperatures are given in degrees centigrade, and all partsand percentages are by weight.

PREPARATION OF NOVOLAK RESIN USING AN UNSUBSTITUTED PHENOL MONOMERExample 1

A phenol-formaldehyde novolak resin was prepared by reacting 0.66 molesof formaldehyde per mole of phenol utilizing 0.25 parts of a sulfuricacid catalyst based on 100 parts of charged phenol. The mixture wassubsequently neutralized, dehydrated to melt, dumped, and allowed tosolidify. The resulting resin has the following properties within thestated ranges:

    ______________________________________                                        Gel Permeation Chromatography (GPC)                                           --Mw                      600-1000                                            --Mn                      350-450                                             Heterogeneity Index (H.I.)                                                                              1.5-2.0                                             Melt Viscosity @ 135 C (centipoises)                                                                    500-1200                                            ______________________________________                                    

100 parts of the solid novolak product was then ground to a fineparticle size and milled with about 21 parts of hexamethylene-tetramine,2 parts of glycerol monostearate, 1 part stearic acid, and 1 part ofzinc stearate.

PREPARATION OF NOVOLAK RESIN USING BISPHENOL-A Example 2

A bisphenol-formaldehyde novolak resin was prepared by reacting 0.66moles of formaldehyde per mole of Bisphenol A utilizing 0.25 parts of asulfuric acid catalyst based on 100 parts of charged Bisphenol A. Themixture was subsequently neutralized, dehydrated to melt, dumped, andallowed to solidify. The resulting resin has the following propertieswithin the stated ranges:

    ______________________________________                                        Gel Permeation Chromatography (GPC)                                           --Mw                      600-1000                                            --Mn                      350-450                                             Heterogeneity Index (H.I.)                                                                              1.5-2.0                                             Melt Viscosity @ 135 C (centipoises)                                                                    500-1200                                            ______________________________________                                    

100 parts of the solid resin product was then ground to a fine particlesize and milled with about 21 parts of hexamethylene-tetramine, 2 partsof glycerol monostearate, 1 part stearic acid, and 1 part of zincstearate.

PREPARATION OF PHENOLIC MOLDING COMPOUNDS Example 3

80 parts of the resin of Example 1 and 20 parts of the resin of Example2 were mixed with 34.6 parts of 60 mesh wood flour, 16.3 parts of 100mesh wood flour, 7.7 parts of bark wood flour, 5.8 parts of diatomaceousearth, 13.5 parts of clay, 7.7 parts of lime, and 1.5 parts of blackdye. The compound was ball-milled for 1 hour, roll-milled at 70° C.(front roll) and 90° C. (back roll), and ground thru a 1/4" screen. Ablending wax was added and the resulting molding compound was analyzedusing a Brabender Plasticorder. The results are set forth below in Table1.

Example 4

A phenolic molding compound was prepared following the procedure ofExample 3 using 60 parts of the resin of Example 1 and 40 parts of theresin of Example 2. The results are set forth in Table 1.

Example 5

Following the procedure of Example 3, a phenolic molding compound wasprepared using 40 parts of the resin of Example 1 and 60 parts of theresin of Example 2. The results are set forth in Table 1.

PREPARATION OF NOVOLAK RESIN--IN SITU METHODS Example 6

3000 parts of phenol and 900 parts of Bisphenol A were charged to areaction kettle and heated to 65° C.-75° C. A solution of 2106 parts offormalin (45%) and 9.8 parts of sulfuric acid was added dropwise asrapidly as possible to bring the mixture to reflux. The mixture was heldat reflux temperature until less than about 1% free formaldehyderemained. A solution of 7.4 parts of lime and 20 parts of water was thenadded to neutralize the acid content of the system. The mixture wasvacuum stripped to prepare a brittle base resin. The base resin can thenbe compounded with hexamethylenetetramine, glycerol monostearate,stearic acid, and zinc stearate, such as in Example 1, to prepare amolding compound.

Example 7

1500 parts of phenol was charged to a reaction kettle and mixed with asolution of 1500 parts of acetone, 11.7 parts of pyridine, and 15 partsof HCl, which was added dropwise until dissolved. The mixture wasbrought to reflux and held at reflux temperature until the freeformaldehyde content was less than about 1%. The mixture was thendehydrated to prepare a base resin which can be compounded with variousingredients as in Example 6 to prepare a molding compound.

PREPARATION OF PHENOLIC MOLDING COMPOUNDS Example 8

A typical formulation was prepared by employing a resin blend comprisingapproximately 70% of an unsubstituted phenol-formaldehyde novolak resin,such as prepared in Example 1, and about 30% of a bisphenol-formaldehydenovolak resin, such as prepared in Example 2. Various fillers andadjuvants were added to the resin blend to produce a commercial graderunnerless injection molding material.

Control Example 1

Following the procedure of Example 3, a control was prepared using 100parts of the resin of Example 1. The results are set forth in Table 1.

Control Example 2

Following the procedure of Example 3, a control was prepared using 100parts of the resin of Example 2. The results are set forth in Table 1.

Comparative Example 1

Following the procedure of Example 3, a phenolic molding compound wasprepared using 90 parts of the resin of Example 1 and 10 parts of aBisphenol A monomer. The results are set forth in Table 1.

Comparative Example 2

Following the procedure of Example 3, a phenolic molding compound wasprepared using 80 parts of the resin of Example 1 and 20 parts of aBisphenol A monomer. The results are set forth in Table 1.

                                      TABLE 1                                     __________________________________________________________________________           125° C. ANALYSIS 170° C. ANALYSIS                               MINIMUM                                                                              FLOW   PEAK  CURE                                                                              MINIMUM                                                                              FLOW   PEAK  CURE                              TORQUE DURATION                                                                             TORQUE                                                                              TIME                                                                              TORQUE DURATION                                                                             TORQUE                                                                              TIME                       EXAMPLES                                                                             (m-g)  (mm)   (m-g) (min.)                                                                            (m-g)  (mm)   (m-g) (min.)                     __________________________________________________________________________    Example 3                                                                            300    223    2300  9.8 110    22     1350  1.4                        Example 4                                                                            350    260    2350  10.8                                                                              110    27     1575  1.6                        Example 5                                                                            325    338    2745  11.3                                                                              110    34     1690  1.9                        Control                                                                       Example 1                                                                            275    163    2300  8.1 110    24     1125  1.4                        Control                                                                       Example 2                                                                            200    318    3175  17.9                                                                              100    34     2550  2.7                        Comparative                                                                   Example 1                                                                            275    183    2375  8.4 110    33     1225  1.5                        Comparative                                                                   Example 2                                                                            200    177    2400  8.7  90    31     1200  1.5                        __________________________________________________________________________

The data in Table 1 demonstrates the significant improvement in resinstability at the manifold temperature, i.e. 125° C., achieved by thecompositions of this invention as compared to conventional resinsystems. By way of explanation, the Minimum Torque measurement denotesthe minimum viscosity at the indicated temperature, recorded before theonset of cure of the resin. The Flow Duration is a measure of the timeto onset of cure of the resin, measured in millimeters of flow. The PeakTorque is a measure of the strength or rigidity of the composition underpeak loading conditions.

The composition of Example 3 comprises a resin blend of 80 parts byweight of a conventional phenol-formaldehyde novolak resin and 20 partsby weight of a bisphenol-formaldehyde novolak resin. Since theconventional novolak has approximately 50% of the available theoreticalpara-phenyl linkages bridged, while the bisphenol resin has all of theavailable theoretical para-phenyl linkages bridged, the resulting resinblend corresponds to a novolak resin having about 60% of the availabletheoretical para-phenyl linkages bridged. This can be calculated asfollows:

    ______________________________________                                                  80 parts Ex. 1 resin × 50% para linkages                      +         20 parts Ex. 2 resin × 100% para linkages                     =        100 parts Ex. 3 resin × 60% para linkages.                     ______________________________________                                    

Similarly, the composition of Examples 4 and 5 correspond to a novolakresin having 70% of available theoretical para-phenyl linkages bridged,and 80% of the available theoretical para-phenyl linkages bridged,respectively, calculated as follows:

    ______________________________________                                                  60 parts Ex. 1 resin × 50% para linkages                      +         40 parts Ex. 2 resin × 100% para linkages                     =        100 parts Ex. 4 resin × 70% para linkages.                               40 parts Ex. 1 resin × 50% para linkages                      +         60 parts Ex. 2 resin × 100% para linkages                     =        100 parts Ex. 5 resin × 80% para linkages                      ______________________________________                                    

The Cure Time data in Table 1 demonstrates that the compositions ofExamples 3, 4 and 5 exhibit significantly improved resin processingstability at 125° C. as compared to the compositions of Control Example1, and Comparative Examples 1 and 2 which employ a Bisphenol A monomer.The composition of Control Example 2, while exhibiting excellentstability at 125° C., has a molding cycle which is unacceptably long fortypical commercial applications.

PREPARATION OF RESINS BY IN SITU METHOD AND PHENOLIC MOLDING COMPOUNDSPREPARED THEREFROM Example 9

3600 parts of phenol, 400 parts of bisphenol-A, 350 parts of Ashland 10TF solvent which is a mixture of about 47% aliphatic petroleum naphthas,17% toluene and 36% isobutylacetate, and 10 parts of sulfuric acid werecharged to a reaction kettle equipped with a Dean Stark trap andsub-surface feed line. The reactants were mixed and heated to 105°-110°C. Then, 1600 parts of 50 percent aqueous formaldehyde were introducedthrough the sub-surface feed line at a rate to maintain the temperatureat 105°-110° C. The top layer in the trap was returned to the kettle.The reaction was continued at 105°-110° C. for one hour after theformaldehyde addition. The reaction mixture was neutralized slowly witha slurry of 6.5 parts magnesium oxide and 30 parts of water, and mixingwas continued for 5 minutes. The reaction mixture was vacuum strippeduntil it had a brittle point of 63°-70° C. clear. 4000 parts of productwere discharged from the reactor, tested and had the followingproperties:

    ______________________________________                                        Gel Permeation Chromatography (GPC)                                           --Mw                    587                                                   --Mn                    340                                                   Heterogeneity Index (H.I.)                                                                            1.73                                                  Melt Viscosity @ 135° C. (centipoises)                                                         387                                                   ______________________________________                                    

2500 parts of the resin were compounded with 525 parts ofhexamethylenetetramine (hexa), 50 parts of glycerol monostearate, 25parts of stearic acid and 25 parts of zinc stearate. Then 1300 parts ofthe resulting compound was mixed with 450 parts of 60 mesh wood flour,212 parts of 40 mesh wood flour, 100 parts of bark wood flour, 75 partsof diatomaceous earth, 175 parts of clay, 100 parts of magnesium oxide,and 20 parts of black dye. The resulting compound was ball milled forone hour, roll milled at 70° C. (front roll) and 90° C. (back roll) andground through a 1/4 inch screen. A blending wax was added and theresulting molding compound was analyzed using a Brabender plasticorder.The results are shown in Table 3.

Examples 10-14

The processes of Example 9 were repeated using the same proportions andconditions except as shown in Table 2. Resin characteristics are alsoshown in Table 2.

                  TABLE 2                                                         ______________________________________                                                   EXAMPLE NO.                                                                   10    11      12      13    14                                     ______________________________________                                        Phenol       3200    2400    1200  800   400                                  Bisphenol-A  800     1200    2800  3200  3600                                 50% Formaldehyde                                                                           1500    1300    800   800   800                                  Magnesium Oxide                                                                            6.5     6.5     6     6     6                                    Water        30      30      25    25    25                                   Yield of Resin                                                                             4000    4250    3985  4085  4250                                 Initial Heating                                                                            105-    105-    110-  110-  110-                                 Temperature  110     110     115   115   115                                  GPC: --Mw    643     694     463   478   606                                     --Mn      342     360     297   303   353                                     H.I.      1.88    1.93    1.56  1.58  1.72                                 Melt Viscosity @                                                              135° C. (centi-                                                        poises)      650     625     200   437   950                                  ______________________________________                                    

In Examples 12, 13 and 14, the final compound was prepared by mixing 390parts of the hexa-resin compound of the respective Example with 910parts of a hexa-resin compound made with a phenolic novolak such asprepared in Example 1.

                                      TABLE 3                                     __________________________________________________________________________           125° C. ANALYSIS 170° C. ANALYSIS                               MINIMUM                                                                              FLOW   PEAK  CURE                                                                              MINIMUM                                                                              FLOW   PEAK  CURE                              TORQUE DURATION                                                                             TORQUE                                                                              TIME                                                                              TORQUE DURATION                                                                             TORQUE                                                                              TIME                       EXAMPLE                                                                              (m-g)  (mm)   (m-g) (min.)                                                                            (m-g)  (mm)   (m-g) (min.)                     __________________________________________________________________________     9     400    271    2250  10.0                                                                              125    23     1075  1.28                       10     425    275    2150  10.3                                                                              125    24     1100  1.28                       11     400    315    2500  12.28                                                                             125    25     1250  1.4                        12     475    265    2500  9.95                                                                              110    22     1125  1.32                       13     500    251    2500  9.55                                                                              125    22     1180  1.28                       14     500    234    2500  8.98                                                                              125    21     1150  1.28                       __________________________________________________________________________

Example 15

3200 parts of phenol, 800 parts of bisphenol-A, 1400 parts of tolueneand 20 parts of sulfuric acid were charged to a reaction kettle equippedwith a Dean Stark trap and a sub-surface feed line. The reactants weremixed and heated to 115° C. Then, 1803 parts of isobutyraldehyde wereadded through the sub-surface feed line at a rate to maintain thetemperature at 110°-115° C. The top layer in the trap was returned tothe kettle. The reaction was continued at 110°-115° C. for two hoursafter addition of the isobutyraldehyde. The reaction mixture wasneutralized slowly with a slurry of 15 parts of lime and 45 parts ofwater. Thereafter, the reaction mixture was vacuum stripped until it hada brittle point of 63°-70° C. clear. 4890 parts of product weredischarged from the reactor.

3000 parts of the resin were compounded with 630 parts ofhexamethylenetetramine (hexa), 30 parts of stearic acid, 30 parts ofzinc stearate and 60 parts of glycerol monostearate.

Examples 16 and 17

The processes in Example 15 were repeated for Examples 16 and 17 usingthe same proportions and conditions except as shown in Table 4. Resincharacteristics are also shown in Table 4.

                  TABLE 4                                                         ______________________________________                                                  EXAMPLE NO.                                                                   15       16         17                                              ______________________________________                                        Phenol      3200       2400       1600                                        Bisphenol-A 800        1600       2400                                        Isobutyraldehyde                                                                          1803       1563       1323                                        Yield       4890       4275       4435                                        GPC: --Mw   375        344        335                                            --Mn     280        276        269                                            H.I.     1.34       1.25       1.24                                        Melt Viscosity                                                                (CP @ 135° C.)                                                                     400        363        513                                         ______________________________________                                    

For each of the hexa-resin compounds of Examples 15, 16 and 17, threeblends of the hexa-resin compounds of the respective Example was blendedwith the hexa-resin compound as produced in Example 1. These blends wereprepared in the proportions shown in Table 5.

                  TABLE 5                                                         ______________________________________                                                       SAMPLE CODE                                                                   A      B        C                                              ______________________________________                                        Resin of Example 250      500      750                                        Resin of Example 1                                                                             750      500      250                                        ______________________________________                                    

Each of the three blends for each of the three Examples (total of 9blends) was compounded with 346 parts of 60 mesh wood flour, 163 partsof 40 mesh wood flour, 77 parts of bark wood flour, 58 parts ofdiatomaceous earth, 35 parts of clay, 77 parts of Code 11 and 15 partsof black dye. The resulting compound was ball-milled for one hour,roll-milled at 70° C. (front roll) and 90° C. (back roll) and groundthrough a 1/4 inch screen. A blending wax was added and the resultingmolding compound was analyzed using a Brabender plasticorder. Theresults are shown in Table 6.

                                      TABLE 6                                     __________________________________________________________________________           125° C. ANALYSIS 170° C. ANALYSIS                               MINIMUM                                                                              FLOW   PEAK  CURE                                                                               MINIMUM                                                                             FLOW   PEAK  CURE                              TORQUE DURATION                                                                             TORQUE                                                                              TIME                                                                              TORQUE DURATION                                                                             TORQUE                                                                              TIME                       EXAMPLE                                                                              (m-g)  (mm)   (m-g) (min.)                                                                            (m-g)  (mm)   (m-g) (min.)                     __________________________________________________________________________    15 A   350    364    475   13.5                                                                              125    23     1825  1.6                        15 B   300    552    720   20.2                                                                              100    29     2400  2.25                       15 C   200    >1180        >29.5                                                                              85    52     3450  3.0                        16 A   400    414    520   14.8                                                                              115    29     1900  1.8                        16 B   300    612    815   23.1                                                                              100    40     2350  2.3                        16 C   225    --     --    >30.                                                                               65    50     3400  3.4                        17 A   345    419    550   14.7                                                                              110    28     1750  1.87                       17 B   300    650    680   23.0                                                                              100    44     2250  2.5                        17 C   225    --     --    >30.0                                                                              75    59     2950  3'57"                      __________________________________________________________________________

The foregoing embodiments are intended to illustrate the inventionwithout limiting it thereby. Various modifications can be made in theinvention without departing from the spirit and scope thereof.

I claim:
 1. In a runnerless injection molding process wherein athermosetting resin is fused in the manifold of a runnerless injectionmolding apparatus and cured in a mold cavity, the improvement whichcomprises employing as the thermosetting resin component, a phenolicnovolak molding composition comprising a phenol-aldehyde resin wherein(a) from about 55% to about 90% of the available theoretical para-phenyllinkages in the resin chain are bridged to a phenyl group, (b) thecarbon chains linked between adjacent hydroxyl-substituted phenyl nucleihave 1 to 5 carbon atoms, and (c) the hydroxyl-substituted phenyl nucleiare capable of chain growth at unsubstituted ortho and para-positions ofsaid nuclei; hexamethylenetetramine, and a filler material.
 2. Theprocess of claim 1 wherein the thermosetting resin is prepared in situby the condensation reaction of an unsubstituted phenol, a bisphenol,and an aldehyde.
 3. The process of claim 1 wherein the thermosettingresin is prepared in situ by the sequential reaction of phenol, acetoneand formaldehyde.
 4. The process of claims 2 or 3 wherein the aldehydeis formaldehyde.
 5. The process of claim 2 wherein the bisphenol isbisphenol-A.